DESCRIPTION: (Applicant's Description) This core will provide monoclonal antibody production for members of this Program grant. The overall goal of this Program is to elucidate the functional roles of a number of key proteins that participate in breast development and breast carcinogenesis. High quality antibodies are essential reagents needed to study these proteins. We have developed a productive and highly efficient core for the production of monoclonal antibodies, and this core will provide this service for the participating investigators of this Program grant. The resulting antibodies will be available to members of this Program grant and through them to the research community as a whole.